Climate change has Montana trout swimming to safety

The bull trout is named for its large and uniquely shaped head and mouth.

U.S. Fish and Wildlife Service

In Montana, The Wilderness Society is fighting an upstream battle to save the West’s bull trout and westslope cutthroat trout from the damaging effects of climate change.

A warming climate is making some of Montana’s mountain streams too hot to handle for native trout. As temperatures rise, these important fish are being forced to flee their historic stomping-grounds in order to survive. Our scientists are working hand-in-hand with public land managers to pioneer climate adaptation tools needed to address these challenges, and, whenever possible, to eliminate major climate threats.

Two iconic species in jeopardy

The bull trout, named for its large and uniquely shaped head and mouth, is listed as a threatened species throughout its natural range under the U.S. Endangered Species Act. Bull trout can be differentiated from other trout species by the absence of distinct spots on their dorsal fin, as well as yellow, orange or salmon-colored spots on their back.

The westslope cutthroat trout is perhaps best known for being Montana’s state fish. This beautiful fish gets its name from the unmistakable reddish-orange marking beneath its jaw, and subsists on a diet of mainly insects and zooplankton.

Westslope cutthroat trout. Photo: U.S. Fish and Wildlife Service

Both fish are considered “indicator species” by ecologists, because their presence indicates healthy stream and ecosystem conditions for many species—not just native trout.

So when scientists noticed bull trout and westslope cutthroat trout succumbing to rising stream temperatures, they knew something was seriously amiss.      

What are the risk factors?

America’s Northern Rockies region receives less snow each year, on average, now than it has for the past 60 years. Montana’s annual spring runoff of melting mountain snow is also occurring three to four weeks earlier than usual. Less snow and earlier runoffs mean that late summer stream flows are often significantly reduced—and several degrees warmer—than they were just a century ago.

These habitat changes are very stressful for fish. In particular, Montana’s bull trout and westslope cutthroat trout depend on extremely cold water to breed, feed and migrate. Thanks to climate change, both species are now being forced to seek refuge in new habitats.

Finding a way to cooler stream waters at higher elevation can be a challenge for native trout, however.  Thousands of miles of dirt roads criss-cross forests that grow on our public lands and have the potential to dump excess sediment into streams. Sediment pollution can clog the gills of baby bull trout and contaminate streams, resulting in poor habitat for the aquatic invertebrates that adult fish feed on.

Furthermore, old culverts (manmade passageways that allow vehicles to cross streams) may block the way for trout seeking to move through their mountain habitats. 

Combined, these obstacles can make it nearly impossible for trout to make their way to cooler waters without dedicated efforts to remove these obstacles by scientists, land managers and conservation groups.

The solution: Climate adaptation

Solving these problems, and increasing the resilience of native trout to climate change impacts, requires many different approaches. The Wilderness Society has spent the last five years working to develop and test climate adaptation in Montana’s mountain landscapes, as part of a visionary and dedicated team of university and agency scientists from across the West.

One of the most effective ways that public lands managers can give bull trout and westslope cutthroat trout a fighting chance in the face of climate change is by minimizing major stressors, other than climate change, to both species. By literally clearing the way for native trout, ecologists and land managers are able to guide these fish to waters that can sustain their needs and ensure that their populations will endure for generations to come.

(Left) A watershed where 400 miles of roads (depicted in brown) run alongside streams (shown in blue).

To aid this effort, the Wilderness Society has teamed up with a wide range of partners—from the U.S. Forest Service to local universities, conservation partners, state agencies and community groups—and applied for federal grants to restore watersheds and remove roads across 1.5 million acres of Forest Service lands in Montana.

Our scientists have also been working out in the field to develop mapping technology that will help local officials identify the roadways that are most negatively affecting native trout populations. These new monitoring tools can pinpoint the places where soil is rapidly leaving the forest roads, and allows land managers to track exactly how much sediment is running down the hillsides and into streams. 

(Right) Map showing the same watershed as above, but with major sources of sediment moving from roads into streams identified by red circles: the bigger the circle, the more soil entering the stream each year.

With these tools, land managers may decide to replace an old culvert, for example, or to build a bridge, close a road, or even move a road segment away from a trout stream. They will know how much it costs to resolve the problems where the trout actually live. These tools are revolutionizing the fight for the trout and against climate change.

Response to The Wilderness Society’s climate adaptation work has been very enthusiastic. In November, 2013, the Regional Forester in the Northern Rockies announced an intention to apply these tools across the entire region, which has the potential to dramatically and positively change the way Montana’s public lands and fisheries are managed for many decades to come. 

Climate change is changing wildlife habitats in historically new ways. But The Wilderness Society is working alongside fisheries biologists, aquatic ecologists, and hydrologists to help wildlife populations, like the trout of the Northern Rockies, continue to thrive in spite of a warming climate. 

This is, perhaps, the most important lesson of climate change: Together, we can make a difference.

[Maps and data analyses courtesy of Tom Black and Richard Cissel of the U.S. Forest Service.]